What is the Merkaba Symbol?

PDF download Download Article
All you need to know about the ancient symbol
PDF download Download Article

The Merkaba is a three-dimensional star that has eight points. Its name comes from the ancient Egyptian language, which can be broken into three parts: "Mer" for light, "Ka" for spirit, and "Ba" for the body. The Merkaba is much more than a simple star shape though—it holds deep spiritual significance.The Merkaba is believed by some to be a divine vehicle that helps maintain balance. For centuries, people have sought to unravel the mysteries and meaning behind this sacred geometric symbol. Curious to learn more? Read on for some insight into its history and spiritual healing properties.

What is the meaning of the Merkaba symbol?

The Merkaba, a star-shaped symbol in sacred geometry, symbolizes the balance, stability, and integration of masculine (logic and rationality) and feminine (emotion and intuition)—an important harmony for spiritual growth and aligning with one's true purpose.

Section 1 of 6:

What is the Merkaba Symbol?

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/9\/9d\/Merkaba-Meaning-Step-1.jpg\/v4-460px-Merkaba-Meaning-Step-1.jpg","bigUrl":"\/images\/thumb\/9\/9d\/Merkaba-Meaning-Step-1.jpg\/v4-728px-Merkaba-Meaning-Step-1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    The Merkaba is a physical representation of the union of spirit and body. Commonly depicted as a star tetrahedron (or triangular pyramid), the Merkaba consists of overlapping circles forming a flower-like grid. This symbol is surrounded by light and believed by spiritualists to create an energetic field throughout the universe. [1]
    • Many people use the Merkaba in meditation and breathing exercises as a form of healing, as it's said to bring balance to our inner being. [2]
    2. Advertisement
Section 2 of 6:

History and Origin of the Merkaba

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/c\/c8\/Merkaba-Meaning-Step-2.jpg\/v4-460px-Merkaba-Meaning-Step-2.jpg","bigUrl":"\/images\/thumb\/c\/c8\/Merkaba-Meaning-Step-2.jpg\/v4-728px-Merkaba-Meaning-Step-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    The idea for the word "Merkaba" is derived from the Hebrew Bible, specifically from the text in Ezekiel 1:4-26. While the word itself does not appear explicitly in this passage, the term "chariot" is mentioned numerous times. In this context, it refers to the chariot or throne of God described in Ezekiel's vision. Scholars suggest that this "chariot" should not be interpreted literally, but rather as a representation of how God and his archangels are revealed in the physical world. [3]
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/4\/4b\/Merkaba-Meaning-Step-3.jpg\/v4-460px-Merkaba-Meaning-Step-3.jpg","bigUrl":"\/images\/thumb\/4\/4b\/Merkaba-Meaning-Step-3.jpg\/v4-728px-Merkaba-Meaning-Step-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Derived from the three elements "Mer” (light), "Ka” (spirit), and "Ba" (body), this symbol carries both religious and spiritual significance. [4]
    • The Chabbadic Jewish tradition associates the Merkaba with contemplating personal growth and betterment, which aligns with the concepts of spirituality and sacred geometry. [5]
    3. Advertisement
Section 3 of 6:

The Merkaba and Sacred Geometry

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/f\/fb\/Merkaba-Meaning-Step-4.jpg\/v4-460px-Merkaba-Meaning-Step-4.jpg","bigUrl":"\/images\/thumb\/f\/fb\/Merkaba-Meaning-Step-4.jpg\/v4-728px-Merkaba-Meaning-Step-4.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    The world around us is made up of geometric patterns that form the unique structures of life—from the molecules of our DNA and the corneas of our eyes, to snowflakes, flower petals, crystals, seashells, the stars, the galaxy we inhabit, and even the air we breathe. All life forms emerge from these intricate geometric patterns. For centuries, these patterns, called sacred geometry, have been said to symbolize the interconnected relationship between all things. [6]
    • These symbols draw from ancient traditions and religions, and are revered for their diverse purposes. Each symbol carries its own unique story and meaning. Ultimately, these symbols tend to focus on themes of personal growth, inner peace, and higher consciousness. [7]
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/3\/3b\/Merkaba-Meaning-Step-5-Version-2.jpg\/v4-460px-Merkaba-Meaning-Step-5-Version-2.jpg","bigUrl":"\/images\/thumb\/3\/3b\/Merkaba-Meaning-Step-5-Version-2.jpg\/v4-728px-Merkaba-Meaning-Step-5-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Sometimes referred to as the star tetrahedron, the Merkaba sign resembles a star composed of two counter-rotating tetrahedrons (it looks like a three-dimensional version of the Star of David), which are triangular pyramids. In sacred geometry, the two spinning tetrahedrons, rotating in opposite directions, are said to generate a perfectly balanced energy field. [8]
    • The upward-pointing tetrahedron symbolizes masculine energies and spins in a clockwise motion. [9]
    • The bottom tetrahedron represents feminine energy and rotates counterclockwise. [10]
    • The upward-pointing aspect is said to elevate us spiritually, while the downward-facing point anchors us to the earth, grounding our metaphysical journeys. [11]
  3. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/b\/b1\/Merkaba-Meaning-Step-6.jpg\/v4-460px-Merkaba-Meaning-Step-6.jpg","bigUrl":"\/images\/thumb\/b\/b1\/Merkaba-Meaning-Step-6.jpg\/v4-728px-Merkaba-Meaning-Step-6.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    The Merkaba is everywhere throughout the natural world—present in the molecular patterns of our water, cells, plants, and animals, as if designed by the very fabric of the universe. This shape's origins are deeply tied to the flower of life, the mandala, and the tree of life. [12]
    • Sacred geometric shapes are said to be aligned with divine significance, or can facilitate a connection to higher consciousness or God. [13]
    4. Advertisement
Section 4 of 6:

How is the Merkaba used in spirituality?

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/9\/94\/Merkaba-Meaning-Step-7.jpg\/v4-460px-Merkaba-Meaning-Step-7.jpg","bigUrl":"\/images\/thumb\/9\/94\/Merkaba-Meaning-Step-7.jpg\/v4-728px-Merkaba-Meaning-Step-7.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    The Merkaba is believed to be a tool that can facilitate light-seeking and deep healing. Many believe it can enable access to higher dimensions and encourage the embrace of unconditional love—offering transformative potential for those who welcome its influence. [14]
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/9\/97\/Merkaba-Meaning-Step-8.jpg\/v4-460px-Merkaba-Meaning-Step-8.jpg","bigUrl":"\/images\/thumb\/9\/97\/Merkaba-Meaning-Step-8.jpg\/v4-728px-Merkaba-Meaning-Step-8.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Working with the Merkaba is said to help restore flow to the pineal gland. This gland, located at the center of the forehead, is also known as the third eye chakra. [15]
    • Activating the pineal gland is believed to unlock our full potential, granting access to higher realms, enhancing visualization skills, and deepening our spiritual awareness. [16]
  3. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/b\/be\/Merkaba-Meaning-Step-9.jpg\/v4-460px-Merkaba-Meaning-Step-9.jpg","bigUrl":"\/images\/thumb\/b\/be\/Merkaba-Meaning-Step-9.jpg\/v4-728px-Merkaba-Meaning-Step-9.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    This intricate, sacred star may help restore balance by igniting the activities of the two hemispheres of the brain. By activating both sides of the brain, we can deepen our understanding, enhance our intuition, and open ourselves to new avenues of spiritual growth. [17]
    • Many believe that embracing the Merkaba's magical presence can open our hearts, welcoming the wonder of unconditional love. As this sacred geometric form represents harmony, it can nurture all expressions of love and encourage the awakening of our high-vibrational energy. [18]
  4. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/f\/f1\/Merkaba-Meaning-Step-10.jpg\/v4-460px-Merkaba-Meaning-Step-10.jpg","bigUrl":"\/images\/thumb\/f\/f1\/Merkaba-Meaning-Step-10.jpg\/v4-728px-Merkaba-Meaning-Step-10.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    As the Merkaba is imbued with protective energies, it may also clear any chakra blockages hindering your full potential. Maintaining an unobstructed flow across the seven energy centers of the body facilitates the smooth circulation of our life force. However, this energy can sometimes become stagnant or obstructed, causing us to fall out of balance. As a powerful spiritual force, the Merkaba encourages us to release feelings that may be holding us back. [19]
    5. Advertisement
Section 5 of 6:

Merkaba Meditation

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/0\/02\/Merkaba-Meaning-Step-11.jpg\/v4-460px-Merkaba-Meaning-Step-11.jpg","bigUrl":"\/images\/thumb\/0\/02\/Merkaba-Meaning-Step-11.jpg\/v4-728px-Merkaba-Meaning-Step-11.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Meditating by visualizing a Merkaba is a great way to induce emotional healing. Start by finding a quiet, comfortable spot to sit.
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/5\/56\/Merkaba-Meaning-Step-12.jpg\/v4-460px-Merkaba-Meaning-Step-12.jpg","bigUrl":"\/images\/thumb\/5\/56\/Merkaba-Meaning-Step-12.jpg\/v4-728px-Merkaba-Meaning-Step-12.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Don't worry if it looks different from others—each person's Merkaba is unique. As you clear your mind and focus on the star, begin to imagine it spinning. [20]
  3. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/f\/f3\/Merkaba-Meaning-Step-13.jpg\/v4-460px-Merkaba-Meaning-Step-13.jpg","bigUrl":"\/images\/thumb\/f\/f3\/Merkaba-Meaning-Step-13.jpg\/v4-728px-Merkaba-Meaning-Step-13.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    Visualize the top pyramid pointing towards the heavens and the bottom towards the earth, moving in a synchronized rhythm. [21]
  4. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/b\/b0\/Merkaba-Meaning-Step-14.jpg\/v4-460px-Merkaba-Meaning-Step-14.jpg","bigUrl":"\/images\/thumb\/b\/b0\/Merkaba-Meaning-Step-14.jpg\/v4-728px-Merkaba-Meaning-Step-14.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    As the stars spin faster, feel yourself being illuminated by rays of luminous energy. Let the spinning accelerate, and be open to sensing a surge of joy, energy or power—this indicates your Merkaba has been awakened, and its vibrations are flowing through you. [22]
    • The experience may feel overwhelming at first, but surrender to the energy and see where it leads.
    5. Advertisement
Section 6 of 6:

Merkaba 18-Step Breathing Technique For Healing

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/0\/0c\/Merkaba-Meaning-Step-15.jpg\/v4-460px-Merkaba-Meaning-Step-15.jpg","bigUrl":"\/images\/thumb\/0\/0c\/Merkaba-Meaning-Step-15.jpg\/v4-728px-Merkaba-Meaning-Step-15.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>\u00a9 2024 wikiHow, Inc. All rights reserved. wikiHow, Inc. is the copyright holder of this image under U.S. and international copyright laws. This image is <b>not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. This image may not be used by other entities without the express written consent of wikiHow, Inc.<br>\n<\/p><p><br \/>\n<\/p><\/div>"}
    This breathing meditation guides you through an 18-step process to connect with your inner self and awaken harmonious vibrations through the power of your breath. First, breathe in through your nostrils, using pranayama technique . Next, create pressure in your abdomen, then your diaphragm, and finally your chest, for a complete, controlled inhalation.
    • 1st Breath: Inhale to open your heart and cultivate love for all. Breathe through both nostrils, allowing the air to fill your stomach, diaphragm, and chest. Exhale slowly. Repeat this process until you feel a sense of compassion.
    • 2nd-5th Breaths: Continue the same breathing pattern as the first breath.
    • 6th Breath: Keep the same breathing style, but take 12 breaths total. The first 6 breaths will help balance your polarities, while the second 6 will clear your electromagnetic field.
    • 7th Breath: Shift the focus to inhaling and storing the love you've built up in your heart. You can release the hold on your breath.
    • 8th Breath: Fully exhale, releasing all the air from your lungs. This helps release stagnant energy.
    • 9th Breath: Shift your breathing focus to the navel region.
    • 10th Breath: Exhale slowly through pursed lips, requiring more control over your breath.
    • 11th Breath: Combine the principles of the 9th and 10th breaths—inhale and exhale through the navel with pursed lips.
    • 12th-13th Breaths: Continue the 11th breathing pattern.
    • 14th Breath: Breathe from your navel up to your sternum, allowing your chest to expand rhythmically.
    • 15th Breath: Relax into your Merkaba experience, breathing gently through your lips.
    • 16th-17th Breaths: Maintain the 15th breath pattern to stabilize your Merkaba.
    • 18th Breath: Allow your higher self to guide your breath as you move through sacred geometry. [23]

Expert Q&A

Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
      Advertisement

      Video

      Tips

      Submit a Tip
      All tip submissions are carefully reviewed before being published
      Submit
      Thanks for submitting a tip for review!

      You Might Also Like

      How to Read Palms
      How to
      Perform Astral Projection
      How to Read Your Marriage Line: Length, Curvature, and Unique Characteristics
      What Do Moles on the Hand Mean? An In-Depth Palmistry Guide
      What Does the Angel Number 1212 Mean?
      How to
      Develop Telekinesis
      What Does the Angel Number 222 Mean?
      Interpreting Candle Flame Meanings: Your Ultimate Guide
      How to
      Find Your Lucky Numbers in Numerology
      How to
      Remove Black Magic Spells
      Angel Number 1010: What It Means & What To Do when You See It
      Angel Number 2323: Why Are You Seeing It & What Does It Mean?
      What Does Angel Number 1818 Mean?
      How to
      Find My Angel Number
      Advertisement

      References

      1. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      2. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      3. ↑ https://study.com/academy/lesson/merkabah-mysticism-overview-history.html
      4. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      5. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      6. ↑ https://destinationdeluxe.com/sacred-geometry-explained-healing-benefits/
      7. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      8. ↑ https://sacredcrafts.medium.com/the-merkaba-4f6f65c3413
      9. ↑ https://chakrapractice.com/what-is-the-merkaba-symbol-how-to-use-it/
      1. ↑ https://chakrapractice.com/what-is-the-merkaba-symbol-how-to-use-it/
      2. ↑ https://chakrapractice.com/what-is-the-merkaba-symbol-how-to-use-it/
      3. ↑ https://www.aurahealth.io/blog/unlocking-the-power-of-the-merkaba-symbol
      4. ↑ https://www.aurahealth.io/blog/unlocking-the-power-of-the-merkaba-symbol
      5. ↑ https://www.aurahealth.io/blog/unlocking-the-power-of-the-merkaba-symbol
      6. ↑ https://www.lebtivity.com/event/third-eye-merkaba-activation
      7. ↑ https://www.lebtivity.com/event/third-eye-merkaba-activation
      8. ↑ https://www.aurahealth.io/blog/unlocking-the-power-of-the-merkaba-symbol
      9. ↑ https://www.aurahealth.io/blog/unlocking-the-power-of-the-merkaba-symbol
      10. ↑ https://chakrapractice.com/what-is-the-merkaba-symbol-how-to-use-it/
      11. ↑ https://www.aurahealth.io/blog/a-guide-to-merkaba-meditation
      12. ↑ https://www.aurahealth.io/blog/a-guide-to-merkaba-meditation
      13. ↑ https://www.aurahealth.io/blog/a-guide-to-merkaba-meditation
      14. ↑ https://declutterthemind.com/blog/merkaba-meditation/

      About This Article

      Thanks to all authors for creating a page that has been read 489 times.

      Did this article help you?

      Advertisement